[llvm] r323190 - [X86][SSE] LowerBUILD_VECTORAsVariablePermute - fix PSHUFB source/index operand ordering

[Simon Pilgrim via llvm-commits]

Author: rksimon
Date: Tue Jan 23 03:39:06 2018
New Revision: 323190

URL: http://llvm.org/viewvc/llvm-project?rev=323190&view=rev
Log:
[X86][SSE] LowerBUILD_VECTORAsVariablePermute - fix PSHUFB source/index operand ordering

As detailed in rL317463, PSHUFB (like most variable shuffle instructions) uses Op[0] for the source vector and Op[1] for the shuffle index vector, VPERMV works in reverse which is probably where the confusion comes from.

Differential Revision: https://reviews.llvm.org/D42380

Modified:
    llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
    llvm/trunk/test/CodeGen/X86/var-permute-128.ll

Modified: llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86ISelLowering.cpp?rev=323190&r1=323189&r2=323190&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86ISelLowering.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86ISelLowering.cpp Tue Jan 23 03:39:06 2018
@@ -7903,8 +7903,9 @@ LowerBUILD_VECTORAsVariablePermute(SDVal
         DAG.getNode(ISD::INSERT_SUBVECTOR, SDLoc(SrcVec), VT, DAG.getUNDEF(VT),
                     SrcVec, DAG.getIntPtrConstant(0, SDLoc(SrcVec)));
   }
-  return DAG.getNode(VT == MVT::v16i8 ? X86ISD::PSHUFB : X86ISD::VPERMV,
-                     SDLoc(V), VT, IndicesVec, SrcVec);
+  if (VT == MVT::v16i8)
+    return DAG.getNode(X86ISD::PSHUFB, SDLoc(V), VT, SrcVec, IndicesVec);
+  return DAG.getNode(X86ISD::VPERMV, SDLoc(V), VT, IndicesVec, SrcVec);
 }
 
 SDValue

Modified: llvm/trunk/test/CodeGen/X86/var-permute-128.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/var-permute-128.ll?rev=323190&r1=323189&r2=323190&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/var-permute-128.ll (original)
+++ llvm/trunk/test/CodeGen/X86/var-permute-128.ll Tue Jan 23 03:39:06 2018
@@ -207,13 +207,12 @@ define <8 x i16> @var_shuffle_v8i16(<8 x
 define <16 x i8> @var_shuffle_v16i8(<16 x i8> %v, <16 x i8> %indices) nounwind {
 ; SSSE3-LABEL: var_shuffle_v16i8:
 ; SSSE3:       # %bb.0:
-; SSSE3-NEXT:    pshufb %xmm0, %xmm1
-; SSSE3-NEXT:    movdqa %xmm1, %xmm0
+; SSSE3-NEXT:    pshufb %xmm1, %xmm0
 ; SSSE3-NEXT:    retq
 ;
 ; AVX-LABEL: var_shuffle_v16i8:
 ; AVX:       # %bb.0:
-; AVX-NEXT:    vpshufb %xmm0, %xmm1, %xmm0
+; AVX-NEXT:    vpshufb %xmm1, %xmm0, %xmm0
 ; AVX-NEXT:    retq
   %index0 = extractelement <16 x i8> %indices, i32 0
   %index1 = extractelement <16 x i8> %indices, i32 1